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1. Core: Improve hardness, scratch resistance, and wear resistance

Alpha phase white corundum micro powder is the preferred choice for industrial wear-resistant paint, flooring, and engineering machinery topcoat

Mechanism: Hard particles are embedded in the resin network, and during friction, the particles bear the load, reducing the resin from being cut or scratched;

Effect: Pencil hardness decreases significantly from H to 3H~5H, Taber wear resistance decreases significantly, and it is resistant to stone bumps and steel wool scratches;

Selection: White corundum; Brown corundum is cheap, but it contains iron and is prone to yellowing. It is used for dark wear-resistant paints

Pits: Poor dispersion, loose particles, and instead like sandpaper, the more it grinds, the more it damages the paint film.

✅ 2. Fill pores to increase density → improve water resistance, salt spray resistance, and water whitening resistance

Gamma nano alumina is the mainstay of this application, which perfectly matches the initial/mid-term water resistance and water-resistant white that you were concerned about earlier:

· The size of nano particles is very small, drilling the micropores left by lotion film forming, plugging the “mesh”, cutting off the water, water vapor, salt ion permeation channels;

Direct benefits: reduce water absorption, improve initial water resistance, and reduce reversible whitening; Simultaneous improvement of salt spray and anti-corrosion performance;

Difference: Ordinary micron alumina is more of a skeleton, while nano alumina is the “microporous sealing”;

Limitations: Dispersion is the lifeline, but after aggregation, it becomes a defect, prone to whitening, fogging, and poor water resistance.

✅ 3. Weather resistant, UV resistant, and anti powdering

Alumina has strong chemical inertness, is stable under ultraviolet light, can scatter ultraviolet light, and protects the resin from degradation:

Outdoor steel structures, curtain walls, and photovoltaic protective paint are not prone to powdering, loss of brightness, or fading due to long-term sun exposure;

Comparison between talcum powder and calcium carbonate: Calcium carbonate is prone to acid corrosion and powdering outdoors, while alumina is much more resistant to acid, alkali, and weather

✅ 4. Exclusive functions of powder coating

Extremely low addition amount:

Anti caking, improved powder flowability, and ball rolling effect between powders;

Equipped with a positive charge, it increases the powder loading rate on the friction gun, improves the Faraday cage effect, and provides better powder loading at the corners;

Assisted leveling to reduce pinholes and shrinkage cavities

✅ 5. Thermal conductivity and insulation

High insulation and thermal conductivity superior to resin, used for insulation paint, heat dissipation coating, and electronic protective paint;

Non conductive, suitable for topcoats that require insulation

✅ 6. Adjust matte and anti slip texture

Coarse grained alumina:

Make anti slip flooring and anti slip topcoat;

Cooperate with matting powder to control matte, wear-resistant matting, which is much stronger than the wear resistance of gas-phase silica; Disadvantages: Coarse particles can reduce transparency, and varnish cannot be coated with coarse powder.

✅ 7. Auxiliary pigments/fillers

High purity calcined alumina has high whiteness, low iron content, and will not yellow. It can be compounded with titanium dioxide to improve coverage and reduce costs, making it suitable for light colored industrial paints.

❌ Formula pain points

1. Difficult to disperse and prone to agglomeration and sedimentation: the surface of alumina has many hydroxyl groups, and the pH of the aqueous system is sensitive; Acidity carries a positive charge, alkalinity carries a negative charge, and if the pH is not correct, it will directly coagulate; Nano alumina is particularly severe, and high-speed stirring alone is not enough. It must be sandblasted and modified with suitable dispersants/silane coupling agents

2. High oil absorption value: Adding too much will increase viscosity, consume resin, and make the paint film brittle;

Micro sized white corundum is generally added at a rate of 5-15%;

Nano gamma alumina is generally 1-4%, and adding more can easily cause fogging and decrease transparency

3. Abrasion equipment: Alpha corundum has extremely high hardness, and long-term grinding will wear down the sand grinding cylinder, grinding beads, and pump body

4. Cannot be flame retardant: Aluminum oxide itself does not decompose into water; Aluminum hydroxide ATH is the halogen-free flame retardant filler, capable of high-temperature dehydration, heat absorption, and flame retardancy.

Alpha alumina: featuring wear-resistant, scratch resistant, anti slip, opaque, floor/construction machinery wear-resistant topcoat

Gamma nano alumina: filling micropores, improving water and white resistance, transparency and scratch resistance, powder assisted flow, water-based varnish, high gloss topcoat, UV paint

Aluminum Hydroxide ATH: Flame retardant, smoke suppressant, fire-resistant coating, with completely different functions from alumina

To improve water resistance and initial water resistance, priority should be given to modifying gamma nano alumina with a small amount added to block micro pores in the paint film, reduce water absorption, and minimize reversible water whitening; Simply wanting wear resistance and not caring about transparency: choose white corundum micro powder; If the water resistance is already qualified but only needs to be soaked in water to turn white, nano alumina is a very common solution, but it must be well dispersed, otherwise it will aggravate the fog white.